Electric circuit breaker



Feb. 19, 1935'. R. J. MEIER 1,992,036

, ELECTRIC CIRCUIT BREAKER Filed Sept. 7, 1933 hwventor: Raymond \J. Meier,

H is Attorneg.

Patented Feb. 19, 1935 I g I 'UNETED STATES PATENT OFFICE ELECTRIC CIRCUIT BREAKER Raymond J. Meier, Stonehurst Hills, Pa., as-

signor to General Electric Company, a corporation bf New York Application September 7, 1933, Serial No. 688,474

4 Claims. (01. 200-466) My invention relates to electric circuit breakcircuit breaker comprising stationary contact ers, more particularly to are interrupting contact structure 1 and a coacting movable contact or structure of circuit breakers of the liquid-break or bridging member 2 arranged to bridge and interoil type. connect the stationary contact structure of two 5 The use of so-called finger contacts for stationsimilar' poles. The aforesaid contact structure 5 ary contact structure of oil circuit breakers, for is immersed and coacts in a suitable insulating example, may involve, under certain conditions, liquid 3, such as oil, operation of the circuit burning of the contacts when the circuit breaker breaker between op and Closed Circuit positions is closed on heavycurrents. In general, finger being effected by vertical movement of lift rod 4.

contacts comprise a pair of opposed contact meme The stationary contact structure is of the well 10 bers or plates resiliently mounted and biased toknown fing yp and Comprises the main wards each other so as resiliently to engage at rent-carrying contacts 5 and the arcing contacts opposite sides thereof a wedge-shaped movable 6, the final contact separation and the initial concontact member, commonly known as the bridgtact n m nt taking plac ween the arc l5 ing contact. The finger contacts are initially ening Co tact 6 a d t e bridging Contact 2 or reagaged at the free or outer ends thereof and spread sons well known in the art. The function of the apart by the bridging member during the ircuit contacts 5 is to carry" the current traversing the closing operation. In the event, however, that circuit breaker when it is normally closed and the the aforesaid oil immersed contacts are closed on Construction of the c ar yin t s y heavy current, contact at the point of initial assume a Suitable orm as r e p t at 20 engagement may result inacertain degree of arcdisclosed and Claimed in Tobey et 81. atent ing and consequent generation of gas between the ,7 a d March 9 0 for E ctric contact tips., The gas pressure so formed tends to w blow apart the finger contacts so as momentarily h a i uptin ta s 6, referring t 25 to separate the same from the bridging member comprise a P i of pp d Contact P a es 25 and cause further arcing and generation of high or fingers 7 resiliently biased towards each other gas pressure within the circuit breaker. This conand suppo t d y Semi-rigid leaf Springs 8- The dition is very undesirable since not only are the main Supporting means for e contactt ucture contacts burned and sometimes damaged by arc- Comprises an adapter 9 Suitably Secured, as y ing but the performance of the circuit breaker is e Clamping a s to e lower end of the 30 less efficient. current lead-in conductor stud 11 of the circuit A principal object of my invention is the probreaker. The lower end of the adapter 9 is provision of improved finger contact structure for oil Vided W 81 depending positioning b ck 12 at circuit breakers and the like which shall substa'ne pp Sides of Which a p d the D- tially eliminate arcing and burning upon closure porting and conducting means for the finger eon- 35 of the contacts on heavy currents and which shall ao s 7- be simple and rugged in construction and efficient The Current-Carrying Connections between the and reliable in operation. adapter 9 and the contacts 7 comprise flexible My invention will be more fully set forth in the pp r strip 3 wh h are p d at ir l w r 40 following description referring to the accompanyends between the correspondi co 7 a d 40 ing drawing, and the features of novelty which members 14 Secured as byriveting to the finger characterize my invention will be pointed out Contactse upp ends of the Conductors with particularity in the claims annexed to and together W the Contact pp are ped forming a part of this specification. to opposite sides of the adapter extension 12 be- Referring to the drawing, Fig; 1 is an elevatween the plate members 15. The finger contact 45 tional, fragmentary view of one pole of an oil construction so far described is well known in the circuit breaker embodying the present invention; art and is generally similar to the construction Fig. 2 is an enlarged end view of the circuit disclosed and claimed in Thumin Patent 1,787,291 breaker contact structure shown in Fig. 1 in the granted December 30, 1930 for Electric switch.

open circuit position; Fig. 3 is a similar view In Fig. 2 the contact structure is illustrated in 50 showing the contact structure in closed circuit the opencircuit position, the closing operation inposition, and Fig. 4 is an enlarged detailed view volving vertical, upward movement of the wedgeof a portion of the contact structure shown in the like bridging member 2 and the consequentpreceding figures. spreading apart of the finger contact members as In Fig. 1 is partially shown one pole of an oil illustrated by Fig. 3. The wedge-like member 2 55 makes initial point contact with the lower extremities or arcing tips 7 of the finger contacts prior to spreading apart of the contacts and it is at this initial stage of contact engagement that burning of the contacts and arcing may result when the contacts are closed against heavy currents. If the initial arcing is severe the finger contacts 7 may be momentarily blown apart by reason of the resulting arc pressure, thereby causing extensive arcing between the finger contacts and the member 2. When the contacts are closed under such conditions they may be badly burned or damaged. Moreover, the high gas pressures generated within the circuit breaker tank are very undesirable.

For the purpose of substantially eliminating burning or arcing upon initial engagement of the contacts when closed against heavy currents, means are provided for applying pressure to the points of initial contact engagement and for shifting said pressure upon complete closure of the contacts. To this end a pair of substantially rigid members 16 are supported by and pivotally mounted in the plates 15, as best illustrated by Fig. 4, the lower end of each member 16 being turned inwardly, as at 16', so as to engage at its tip a corresponding finger contact '7. A pair of leaf springs 1'7 clamped at the upper ends thereof to the adapter assembly by the plates 18 are arranged to engage the members 16 and resiliently bias the same towards each other into engagement with the contact fingers 7 as illustrated in Fig. 2.

The aforesaid adapter assembly including the conductors 13, supports 8, mounting plates 15, leaf spring 17 and clamping plates 18 is suitably clamped together to form a single structure as by through-bolts 2o.

The pivoted support for each member 16, re-

ferring to Fig. 4, comprises simply a T-shaped notch 21 formed at the lower edge of a supporting plate 15 into which is fitted a correspondingly shaped extension 22 of the member 16. The member 16 is, therefore, free to pivot about its support, the extension 22 being held in place by the support 8 on one side and by the leaf spring 17 on the opposite side when the adapter assembly is bolted in position. I

The operation of the contact structure is as follows. When the movable bridging member 2 initially engages the arcing tips 7' closing the circuit the leaf springs 17, through the pivoted rigid members 16, serve to concentrate pressure at the arcing tips 7' where initial contact occurs. Accordingly, the coacting contact surfaces make firm contact at a definite pressure, which in itself reduces contact resistance and minimizes burning. The tendency of the finger contacts to blow apart in case of slight arcing is likewise opposed by the concentration of pressure at the arcing tips.

As the member 2 continues the closing movement after theinitial contact engagement, the finger contacts 7 are gradually spread apart with the result that the lower tips 16' of the mem bers 16 are moved out of engagement with the arcing portions 7.

When the contacts are completely closed, as illustrated in Fig. 3, it is desirable that pressure be applied to the finger contacts, as at the midportions thereof, so that they will properly align themselves with respect. to the coacting fiat surfaces of the bridging member and make uniform contact engagement therewith. Durin'g spreading of the contacts 7, the members 16 are engaged by pins 23 rigidly mounted on the finger contacts at substantially the mid-portions thereof and loosely engaged by the supports 8 for facilitating alignment of the contacts. Accordingly, the pressure exerted by the leaf springs 1'7 is transferred from the arcing tips 7' to the pins 23 for biasing the finger contacts into uniform contact engagement with the sides of the member 2 in the desiredmanner. This shifting of the pressure is made possible by the relation between the pivotal movement of themembers 16 and the combined transverse and angular movement of the finger contacts due to engagement by the wedge-like contact member 2.

It will, therefore, be noted that pressure is a r plied to the arcing tips 7' of the finger contacts both during engagement and separation of the contacts for reducing burning upon closure against heavy currents and for substantially limiting arcing at the tips '7' upon opening of the contacts. During normal closed circuit position, however, the pressure is applied to the finger contacts in the desired manner so as to insure proper alignment and uniform contact engagement.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric circuit breaker comprising a movable contact member, a pair of relatively stationary opposed finger contact members adapted to engage said movable member at opposite sides thereof in the closed circuit position, means normally biasing said finger contacts into uniform contact engagement with said contact member in the closed circuit position, means other than the aforesaid means applying pressure to the tip of each of said finger contact members substantially at the point of initial engagement with said movable member so as to increase the content pressure at said point, and means causing shifting of said pressure from said point in response to closing movement of the contactsv so that said pressure is applied uniformly to bias said finger contact into engagement with said movable memher.

2. An electric circuit breaker comprising a wedge-like contact member, a pair of opposed finger contact members adapted to engage saidsaid finger contact members respectively, a pair of leaf springs fixed with respect to said adapter and resiliently biasing each of said pivoted members towards said finger contact members, said pivoted members arranged so as -to urge the tips of said finger contact members into high pressure contact engagement with said wedge-:like member at the points of initial and final contact engagement, and means carried by said finger contact members causing the bias of said leaf springs to be applied adjacent the mid-portions of said finger contact members in response to closing movement of the contacts.

3. An electric circuit breaker comprising a pair of opposed finger contact members, a movable contact adapted to engage and spread apart said finger members so as to be engaged thereby at opposite sides in the closed circuit position, a spring for applying. pressure to the tip of each finger member during initial engagement thereof with said movable contact, a second spring for biasing each finger contact into uniform contact engagement with said movable contact, said second spring acting substantially at the mid-portion of the finger contact, and means for shifting the pressure from said tips to adjacent the midportions of said finger members upon complete closure of said contacts.

4. An electric circuit breaker comprising a fixed adapter, a pair of opposed finger contact members electrically connected to said adapter, means secured to said adapter for supporting and biasing towards each other said contact members, a movable contact member arranged to engage and spread apart said finger contacts against said bias in the closed circuit position, a rigid member coacting with each finger contact pivotally carried by said adapter, resilient'means arranged to bias each rigid member into engagement with the extremity of said finger contact during the initial closing and final opening operations, said rigid member being moved out of engagement with the extremity of said finger contact during the circuit closing operation, and means for applying the bias of said last-named resilient means to urge said 

